Transmission of some species of internal parasites in horses born in 1990, 1991, and 1992 in the same pasture on a farm in central Kentucky

Studies were conducted on transmission of natural infections of several species of internal parasites in horses born and kept on the same pasture on a farm in central Kentucky. Data for the first year (1989) of a 4 year study on this farm have been published recently. The present research represents the second (1990), third (1991), and fourth (1992) years of the investigation. The number of animals (n = 28) examined varied from eight born in 1990 to ten each born in 1991 and 1992. For each year, examination was made of one horse per month, beginning in June of the year of birth and extending through January (1990) or March (1991 and 1992) the following year. Ages of the horses at necropsy ranged from 87 to 251 days. Major parasites present and months of recovery were: bots - Gasterophilus intestinalis in the mouth September-January and in the stomach August-March; stomach worms - Trichostrongylus axei in August and November, Habronema spp. (immature) in July-November and January, and Habronema muscae in October, January, and February; ascarids - Parascaris equorum in the small intestine and lungs all months; intestinal threadworms - Strongyloides westeri in all months except February; large strongyles - Strongylus vulgaris in the large intestine in all months except July and August and in the cranial mesenteric artery in all months, and Strongylus edentatus in the large intestine in January and in the ventral abdominal wall in all months; pinworms - Oxyuris equi in June and January-March; tapeworms - Anoplocephala perfoliata in August-October and December-March; and eyeworms - Thelazia lacrymalis August-February. Yearly differences and similarities o f infections in the horses are discussed. The value of this type of research is mentioned.